1. Technical Field
The present invention relates to a nonaqueous ink composition for ink jet recording and an ink jet recording method using the nonaqueous ink composition.
2. Related Art
Ink jet printing is a technique for printing images and characters by using small ink droplets discharged from nozzles of an ink jet recording head. Ink jet printing has mainly been used for printing images and characters on a surface of a water-absorbing recording medium such as paper. Aqueous inks produced by adding colorants such as water-soluble dyes to water are widely used as the inks for ink jet printing. However, recent years have seen use of ink jet printing in printing on surfaces of various other types of recording media in various different fields. In order to render the ink jet printing technique suitable for printing on various types of recording media, nonaqueous inks substantially free of water as a solvent have been developed to replace the aqueous inks.
Examples of such nonaqueous inks include those based on glymes (a.k.a. glycol diethers) such as diethylene glycol diethyl ether, glycol dialkyl ethers such as diethylene glycol butyl methyl ether, glycol monoalkyl ethers such as diethylene glycol monobutyl ether, dicarboxylic acid diesters such as dimethyl glutarate, lactones such as γ-butyrolactone, and amide-based solvents such as N-methyl-2-pyrrolidone (for example, refer to Japanese Unexamined Patent Application Publication No. 2009-74034). These nonaqueous inks are designed to firmly fix onto surfaces of vinyl chloride resins and form images and characters that have high water-resistance, lightfastness, and rub resistance.
These nonaqueous inks are formulated based on the assumption that printing is to be conducted on vinyl chloride resins. Thus, it has been necessary to limit the contents of protic polar media. This results in poor proton donor ability and a viscosity close to that of a Newtonian flow. In order to assure ink discharge stability during ink droplet formation (in particular, in the case where high frequency is used) with the ink jet recording method, it is necessary that the ink have a particular degree of pseudoplastic flow behavior. However, as for nonaqueous ink, there has been no adequate materials for imparting pseudoplasticity and it has been difficult to assure good discharge stability.
Moreover, the fixability of the nonaqueous ink onto recording media composed of vinyl chloride resin has not been sufficient and the recorded images sometimes fail to achieve sufficient rub resistance.